Filter on allowed user language preferences (#2361)

* Naive approached to timeline filtering

* Convert allowed_languages into a db column

* Allow users to choose languages to see statuses in

* Style list items as two columns

* Add a hint to explain language filtering preference

app/assets/stylesheets/forms.scss

@@ -326,3 +326,10 @@ code {
     flex: 0 0 auto;
   }
 }
+
+.user_allowed_languages {
+  li {
+    float: left;
+    width: 50%;
+  }
+}